The motivation of frame rate up-conversion is that a video sequence with higher frame rate is generally considered to give higher quality experience than a video sequence with lower frame rate. The frame rate of a video sequence can be increased by inserting predicted frames in between existing frames. A good approach is to predict the in-between frame using bi-directional block based motion estimation, searching for linear motions between the previous frame and the next frame in the input video sequence. It is possible to use non-linear approaches that can represent acceleration, but the linear approach is used because of its simplicity and low complexity. The in-between frame is divided into blocks and to each of these a motion vector must be assigned in some way.
There is a problem with frame rate up-conversion that occurs along the borders of the image. In many recorded video sequences, there is a black line along one or more of the borders. It can be seen along the right border in image 50 to the left in FIG. 1. In traditional rate up-conversion algorithms [1-3], there is no special treatment of such borders. This can have the consequence of assigning motion vectors pointing to the border area, which may cause the line to follow the background motion and move from the edge into the picture, as seen in the middle image 60 in FIG. 1.